Anthem Inc. employees who sued the company over the fees tied to its $5.1 billion 401(k) plan won a court order revamping the case’s class definitions.

The Jan. 24 order gives class treatment to two subclasses: one of Anthem plan investors subject to a revenue sharing fee structure used between 2009 and 2013, and one of investors who paid flat annual fees for plan administration beginning in 2013.

The employees’ revamped class definitions resolve problems that led Judge Tanya Walton Pratt of the U.S. District Court for the Southern District of Indiana to certify only one of their two proposed...